High strength, low temperature NSF certified Lead-free Cadmium-Free Potable water safe solder. Melts at just 430°F / 221°C for strong & ductile joints on Copper and Stainless Steel Convenient Rosin core for one step joints with high tolerance to vibration and stress. Rosin Core 1/16" (1.6mm) diameter x half pound spool Pairs with Kapp Comet Flux when the additional flux is necessary (sold separately) KappZapp3.5R solder contain a central core of Rosin soldering flux to break the oxide layer on the parts, and promote a strong metallic bond between the solder and parts. Rosin is a mildly acidic flux designed for soldering Stainless Steel and Copper parts in electrical and electronic components. The resulting joints have high tolerance to vibration and stress, with tensile strengths to 33,000 psi on Stainless. The flux residue can be is removed with warm water or alcohol and a clean rag or Q-Tip.